Improved Dosimetry with Daily Online Adaptive Radiotherapy for Cervical Cancer: Waltzing the Pear

AIMS

Standard of care radiotherapy for locally advanced cervical cancer includes large margins to ensure the uterocervix remains within the treatment fields over the course of treatment. Daily online cone-beam adaptive radiotherapy corrects for interfractional changes by adjusting the plan to match the target position during each treatment session, thus allowing for significantly reduced clinical target volume (CTV) to planning target volume (PTV) margins. We hypothesise that reduced margins from daily online adaptive radiotherapy will reduce organ at risk dose without compromising target coverage.

MATERIALS AND METHODS

Ten patients with cervical cancer (stage IIB-IIIC2) were treated with definitive chemoradiation using daily online cone-beam adaptive radiotherapy in 25-27 fractions. Initial and all adapted treatment plans were generated with CTV to PTV margins versus standard of care image-guided radiotherapy (IGRT) plans as follows: cervix/uterus/gross tumour volume (0.5 versus 1.5 cm), parametria/vagina (0.5 versus 1.0 cm) and nodal chains and gross nodes (0.5 versus 0.5 cm). IGRT plans were created and copied to synthetic computed tomography scans and contours generated from each daily adapted fraction. The dosimetry of each clinically treated online adapted fraction was compared with emulated IGRT plans. Statistical significance was defined as P < 0.05.

RESULTS

Daily online cone-beam adaptive radiotherapy significantly improves bowel bag dosimetry compared with IGRT, with a reduction in V40 by an average of 91.3 cm3 [V40 (-6.2%) and V45 (-6.1%)]. The daily adapted plans showed significant improvements in bladder and rectum [V40 (-25.2% and -36.0%) and V30 (-9.7% and -17.1%), respectively]. Additionally, bone marrow had a significantly reduced dose [V10 (-2.7%) and V20 (-3.3%)]. Daily online cone-beam adaptive radiotherapy improved uterocervix CTV coverage and reduced hotspots compared with IGRT [D95% (+1.6%) and Dmax (-0.9%)].

CONCLUSIONS

Reduced CTV to PTV margins achievable with daily online adaptive radiotherapy improves organ at risk dosimetry and target coverage when compared with standard of care IGRT for locally advanced cervical cancer. The clinical impact of improved dosimetry is currently undergoing investigation.

Stereotactic Ablative Radiotherapy for the Treatment of Glandular Metastases from Renal Cell Carcinoma

PURPOSE/OBJECTIVE(S)

Glandular metastases including pancreatic and adrenal sites of disease are associated with renal cell carcinoma (RCC) of indolent biology. Adrenal and pancreatic metastases may develop in isolation or involve other organs and are associated with prolonged survival. Glandular metastases can be treated with systemic therapy, stereotactic ablative radiotherapy (SAbR) or surgical resection and the optimal management of these patients is unknown. There is paucity of data on SAbR for RCC glandular metastases. We hypothesize that ablative doses of radiation therapy utilizing SAbR are associated with high rates of local control greater than 90%, with minimal or no acute grade 3 toxicities or higher with this approach. Here, we report local control (LC), progression-free survival (PFS), overall survival (OS) rates as well as toxicities related to SAbR for RCC metastases to the pancreatic and adrenal glands.

MATERIALS/METHODS

This IRB-approved, single-institution, retrospective study included patients with RCC metastases to the adrenal glands and pancreas treated with SAbR. Data on patient demographics, functional status, tumor characteristics, International Metastatic RCC Database Consortium (IMDC) risk category, local and systemic treatments, toxicities, and outcomes were collected and analyzed. RECIST 1.1 principals were utilized to determine LC rates and PFS. PFS was determined from the initiation of SAbR to progression (at SAbR-treated or other sites), or death. OS was defined from the start of SAbR to death. Two independent reviewers assessed these measures and analyzed patient electronic health records for toxicities using CTCAE v5 and relatedness scores.

RESULTS

A total of 50 RCC patients were included in this study with 36 adrenal and 20 pancreatic metastases treated with SAbR. Median dose fractionation used was 40 Gray delivered in 5 fractions. Sixteen patients (32%) were treatment naïve with oligometastatic disease, and thirty-four (68%) were oligo-progressive on systemic therapy with 1-3 prior lines of systemic therapy. For treated adrenal metastatic lesions at 1 year, patients demonstrated a 75.3% OS, 46.7% PFS, and LC of 93.3%. For treated pancreatic metastatic lesions at 1 year, patients demonstrated a 100% OS, 48.6% PFS, and LC of 100%. At 1 year, there was an OS of 82.2%, PFS of 48.2%, and LC of 95.9 % in the combined cohort. The percentage of patients experiencing an acute grade 2 or 3 toxicity attributed to adrenal or pancreatic gland SAbR was 7.4%. There were no acute grade >3 toxicities. The percentage of patients experiencing a late grade 2 or 3 toxicity was 9.3%. Median time to late adverse events was 37.4 months.

CONCLUSION

SAbR of RCC metastases to the pancreas and adrenal glands is feasible, safe and appears to be effective. Median PFS and OS in this cohort compared favorably to those reported in historical cohorts and is consistent with indolent disease.

Enough and Some to Spare: Improved OAR Sparing with Daily Online Cone Beam Adaptive Radiation Therapy (OnC-ART) of the Cervix

PURPOSE/OBJECTIVE(S)

The standard of care treatment for locally advanced cervical cancer involves pelvic chemoradiation. During treatment planning, the cervix and uterus contours are expanded by 1.5 to 2 cm margins to account for inter- and intrafractional motion per the consensus guidelines. Daily online cone-beam adaptive radiation therapy (OnC-ART) accounts for interfractional motion, thus significantly reducing CTV to PTV margins. In this study, we compared the dosimetry of standard larger margin plans (IGRT) to 0.5 cm margins for patients treated with daily OnC-ART and hypothesized that daily OnC-ART with reduced margins will have improved dosimetry.

MATERIALS/METHODS

A retrospective cohort of 10 patients with cervical cancer (stage IIB - IIIC2) treated with 260 definitive daily fractions of OnC-ART chemoradiation between April 2021 and December 2022 was included. Initial plans were generated with OnC-ART and IGRT CTV to PTV margins as follows: combined cervix, uterus, and GTV (0.5 cm vs. 1.5 cm), combined parametria and vagina (0.5 cm vs. 1 cm), nodal chains (0.5 cm vs. 0.5 cm), and gross nodes (0.5 cm vs. 0.5 cm). The initial IGRT plan was copied to synthetic CTs generated for each fraction in the adaptive workflow containing the daily contours of all targets and OARs. The dosimetry of each IGRT fraction was compared to the dose delivered from each daily OnC-ART fraction. Statistical significance was defined as p < 0.05.

RESULTS

When compared with dosimetry from daily IGRT, the daily OnC-ART plans had significantly improved CTV coverage and less hotspots with improvements in D95% (+1.6%), D99% (+2.9%), and Dmax (-0.9%). Bowel bag and bowel loops showed significant improvements in Dmax (-1.4% and - 2.6%), V40 (-6.2% and -5.3%), and V45 (-6.1% and 5.5%). The daily OnC-ART plans had a mean bowel bag V40 of 177.4 cm3. Contrastingly, the mean bowel bag V40 for the large margin IGRT plans was 268.7 cm3. The bladder and rectum also showed significant improvements in Dmax (-1.7% and -1.6%), V40 (-25.2% and -36.0%), and V30 (-9.7% and -17.1%). The daily OnC-ART plans had a mean bladder and rectum V40 of 41.6 cm3 and 18.4 cm3, and the large margin IGRT plans had a mean bladder and rectum V40 of 65.1 cm3 and 40.8 cm3. Bone marrow had a significantly reduced dose with improvements in Dmean (-3.2%), V10 (-2.7%), and V20 (-3.3%).

CONCLUSION

Reduced CTV to PTV margins achievable with daily OnC-ART is shown to not only improve sparing of critical OARs, especially the bladder and rectum, but also improves target coverage compared to larger margins from daily IGRT. The clinical impact of these dosimetric improvements is currently undergoing investigation.

Evaluating the effectiveness of pneumococcal conjugate vaccine in Taoyuan city on adult population

 

Pneumococcus is one of the major threat for senior citizens health worldwide. Pneumococcal Conjugate Vaccines (PCV7, PCV10, and PCV13) were gradually commenced in the national pediatric immunization programme in Taiwan since 2005 and polysaccharide pneumococcal vaccine (PPV23) was granted adult indication since 2015. However, in a most-recent nationwide long-term surveillance, the PCV13 serotypes have shifted to being dominated types in that of &gt; = 65 years-old seniors. This study aims to evaluate the PCV13-introduction effectiveness based on a selected test city. Data of the national health insurance research database (NHIRD) between 2013 and 2018 were retrieved to collect data on yearly medical use of citizen aged 65-66 years and were linked to the death registry database for death-ascertainment. Compared to females, males had more hospitalization due to IPD (RR = 1.37, 95% CI: 1.04-1.79) and due to pneumonia (1.69, 1.34-2.14). The introduction of PCV13 free-vaccination was associated with significant reductions of hospitalization by 40% for IPD (0.6, 0.51-0.71) and 36% for pneumonia (0.64, 0.58-0.7) in females. However, the effects were not significant in both sex combined and in males. As far as mortality is concerned, the introduction of the PCV13 free-vaccination had 33% lower risk of all cause death with IPD claimed within one month of death (0.67, 0.49-0.91) and for pneumonia (0.77, 0.60-0.99). This was also observed in both sex combined (0.82, 0.68-0.98) for IPD, but not for pneumonia, or for both events in males. In conclusion, the policy of PCV13 vaccination for seniors aged 65 years was associated with all-cause mortality with IPD or pneumonia claims one month before death. The evidence was stronger in females than in males. The effectiveness for the associated reduced hospitalization has been demonstrated in females. Further analysis with individual vaccination history and extended years is needed. Funding: The current study was funded by Pfizer Limited (Taiwan).

Key messages

The pneumococcal serotype shift has been found in elderly from PPV-23 vaccine-type to PCV vaccine-type and hence the preparedness of PCV13-introduction for elderly immunization programme is necessary. The findings of this pilot study included the effectiveness of PCV13-introduction in seniors aged 65 years and some implications to subgroup analyses needed for preparing a nationwide implementation.

CRISPR-Cas9 Gene Editing for Sickle Cell Disease and β-Thalassemia

Transfusion-dependent β-thalassemia (TDT) and sickle cell disease (SCD) are severe monogenic diseases with severe and potentially life-threatening manifestations. BCL11A is a transcription factor that represses γ-globin expression and fetal hemoglobin in erythroid cells. We performed electroporation of CD34+ hematopoietic stem and progenitor cells obtained from healthy donors, with CRISPR-Cas9 targeting the BCL11A erythroid-specific enhancer. Approximately 80% of the alleles at this locus were modified, with no evidence of off-target editing. After undergoing myeloablation, two patients - one with TDT and the other with SCD - received autologous CD34+ cells edited with CRISPR-Cas9 targeting the same BCL11A enhancer. More than a year later, both patients had high levels of allelic editing in bone marrow and blood, increases in fetal hemoglobin that were distributed pancellularly, transfusion independence, and (in the patient with SCD) elimination of vaso-occlusive episodes. (Funded by CRISPR Therapeutics and Vertex Pharmaceuticals; ClinicalTrials.gov numbers, NCT03655678 for CLIMB THAL-111 and NCT03745287 for CLIMB SCD-121.).

Corrigendum: Landscape of X chromosome inactivation across human tissues

This corrects the article DOI: 10.1038/nature24265.

Soft X-Ray Tomography Reveals Gradual Chromatin Compaction and Reorganization during Neurogenesis In Vivo

The realization that nuclear distribution of DNA, RNA, and proteins differs between cell types and developmental stages suggests that nuclear organization serves regulatory functions. Understanding the logic of nuclear architecture and how it contributes to differentiation and cell fate commitment remains challenging. Here, we use soft X-ray tomography (SXT) to image chromatin organization, distribution, and biophysical properties during neurogenesis in vivo. Our analyses reveal that chromatin with similar biophysical properties forms an elaborate connected network throughout the entire nucleus. Although this interconnectivity is present in every developmental stage, differentiation proceeds with concomitant increase in chromatin compaction and re-distribution of condensed chromatin toward the nuclear core. HP1β, but not nucleosome spacing or phasing, regulates chromatin rearrangements because it governs both the compaction of chromatin and its interactions with the nuclear envelope. Our experiments introduce SXT as a powerful imaging technology for nuclear architecture.

Pial Artery Supply as an Anatomic Risk Factor for Ischemic Stroke in the Treatment of Intracranial Dural Arteriovenous Fistulas

BACKGROUND AND PURPOSE

Although intracranial dural arteriovenous fistulas are principally supplied by dural branches of the external carotid, internal carotid, and vertebral arteries, they can also be fed by pial arteries that supply the brain. We sought to determine the frequency of neurologic deficits following treatment of intracranial dural arteriovenous fistulas with and without pial artery supply.

MATERIALS AND METHODS

One hundred twenty-two consecutive patients who underwent treatment for intracranial dural arteriovenous fistulas at our hospital from 2008 to 2015 were retrospectively reviewed. Patient data were examined for posttreatment neurologic deficits; patients with such deficits were evaluated for imaging evidence of cerebral infarction. Data were analyzed with multivariable logistic regression.

RESULTS

Of 122 treated patients, 29 (23.8%) had dural arteriovenous fistulas with pial artery supply and 93 (76.2%) had dural arteriovenous fistulas without pial arterial supply. Of patients with pial artery supply, 4 (13.8%) had posttreatment neurologic deficits, compared with 2 patients (2.2%) without pial artery supply (P = .04). Imaging confirmed that 3 patients with pial artery supply (10.3%) had cerebral infarcts, compared with only 1 patient without pial artery supply (1.1%, P = .03). Increasing patient age was also positively associated with pial supply and treatment-related complications.

CONCLUSIONS

Patients with dural arteriovenous fistulas supplied by the pial arteries were more likely to experience posttreatment complications, including ischemic strokes, than patients with no pial artery supply. The approach to dural arteriovenous fistula treatment should be made on a case-by-case basis so that the risk of complications can be minimized.

Systematic chromatin state comparison of epigenomes associated with diverse properties including sex and tissue type

Epigenomic data sets provide critical information about the dynamic role of chromatin states in gene regulation, but a key question of how chromatin state segmentations vary under different conditions across the genome has remained unaddressed. Here we present ChromDiff, a group-wise chromatin state comparison method that generates an information-theoretic representation of epigenomes and corrects for external covariate factors to better isolate relevant chromatin state changes. By applying ChromDiff to the 127 epigenomes from the Roadmap Epigenomics and ENCODE projects, we provide novel group-wise comparative analyses across sex, tissue type, state and developmental age. Remarkably, we find that distinct sets of epigenomic features are maximally discriminative for different group-wise comparisons, in each case revealing distinct enriched pathways, many of which do not show gene expression differences. Our methodology should be broadly applicable for epigenomic comparisons and provides a powerful new tool for studying chromatin state differences at the genome scale.

BRCA1 recruitment to transcriptional pause sites is required for R-loop-driven DNA damage repair

The mechanisms contributing to transcription-associated genomic instability are both complex and incompletely understood. Although R-loops are normal transcriptional intermediates, they are also associated with genomic instability. Here, we show that BRCA1 is recruited to R-loops that form normally over a subset of transcription termination regions. There it mediates the recruitment of a specific, physiological binding partner, senataxin (SETX). Disruption of this complex led to R-loop-driven DNA damage at those loci as reflected by adjacent γ-H2AX accumulation and ssDNA breaks within the untranscribed strand of relevant R-loop structures. Genome-wide analysis revealed widespread BRCA1 binding enrichment at R-loop-rich termination regions (TRs) of actively transcribed genes. Strikingly, within some of these genes in BRCA1 null breast tumors, there are specific insertion/deletion mutations located close to R-loop-mediated BRCA1 binding sites within TRs. Thus, BRCA1/SETX complexes support a DNA repair mechanism that addresses R-loop-based DNA damage at transcriptional pause sites.

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Endogenous BRCA1 and senataxin (SETX) interact in a BRCA1-driven process

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BRCA1/SETX complexes are recruited to R-loop-associated termination regions (TRs)

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BRCA1/SETX complexes suppress transcriptional DNA damage arising at nearby R-loops

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BRCA1 breast cancers reveal indel mutations near BRCA1 TR binding regions

Integrative analysis of 111 reference human epigenomes

The reference human genome sequence set the stage for studies of genetic variation and its association with human disease, but epigenomic studies lack a similar reference. To address this need, the NIH Roadmap Epigenomics Consortium generated the largest collection so far of human epigenomes for primary cells and tissues. Here we describe the integrative analysis of 111 reference human epigenomes generated as part of the programme, profiled for histone modification patterns, DNA accessibility, DNA methylation and RNA expression. We establish global maps of regulatory elements, define regulatory modules of coordinated activity, and their likely activators and repressors. We show that disease- and trait-associated genetic variants are enriched in tissue-specific epigenomic marks, revealing biologically relevant cell types for diverse human traits, and providing a resource for interpreting the molecular basis of human disease. Our results demonstrate the central role of epigenomic information for understanding gene regulation, cellular differentiation and human disease.

The water exchange method for colonoscopy-effect of coaching

The growing popularity of water immersion is supported by its long history as an adjunct to air insufflation; after facilitating colonoscope passage, the infused water is conveniently removed during withdrawal. Water exchange, a modification of water immersion to minimize discomfort in scheduled unsedated patients in the U.S. is new. Even though it may be superior in reducing pain and increasing adenoma detection, the paradigm shift to complete exclusion of air during insertion necessitates removal of infused water containing residual feces, a step often perceived as laborious and time-consuming. The nuances are the efficient steps to remove infused water predominantly during insertion to maintain minimal distension and deliver salvage cleansing. Mastery of the novel maneuvers with practice returns insertion time towards baseline. In this observational study the impact of direct verbal coaching on the primary outcome of intention-to-treat cecal intubation was assessed. The results showed that 14 of 19 (74%) experienced colonoscopists achieved 100% intention-to-treat cecal intubation. Initiation of the examination with water exchange did not preclude completion when conversion to the more familiar air insufflation method was deemed necessary to achieve cecal intubation (total 98%). The overall intention-to-treat cecal intubation rate was 88%, 90% in male and 87% in female. Only 2.7% of bowel preparation was rated as poor during withdrawal. The mean volume of water infused and cecal intubation time was 1558 ml and 18 min, respectively. Direct coaching appears to facilitate understanding of the nuances of the water exchange method. Studies of individual learning curves are necessary.

An epigenetic signature for monoallelic olfactory receptor expression

Constitutive heterochromatin is traditionally viewed as the static form of heterochromatin that silences pericentromeric and telomeric repeats in a cell cycle- and differentiation-independent manner. Here, we show that, in the mouse olfactory epithelium, olfactory receptor (OR) genes are marked in a highly dynamic fashion with the molecular hallmarks of constitutive heterochromatin, H3K9me3 and H4K20me3. The cell type and developmentally dependent deposition of these marks along the OR clusters are, most likely, reversed during the process of OR choice to allow for monogenic and monoallelic OR expression. In contrast to the current view of OR choice, our data suggest that OR silencing takes place before OR expression, indicating that it is not the product of an OR-elicited feedback signal. Our findings suggest that chromatin-mediated silencing lays a molecular foundation upon which singular and stochastic selection for gene expression can be applied.

Crystal Phase Effects in Electrochromic WO3

The electrochromic behavior of crystalline WO3 thin films of two different crystal structures was investigated. The films were deposited on ITO-coated Coming 7059 glass and transparent single crystal sapphire substrates by electron beam evaporation. The usual monoclinic crystal structure was obtained by post-annealing films deposited at low substrate temperatures. An alternative phase was generated by in-situ growth of crystalline films at high substrate temperatures. The reversible electrochemical insertion of Li was demonstrated by cyclic voltammetry. Optical switching was observed by comparing visible transmittance, visible reflectance, and infrared reflectance spectra of films before and after Li intercalation. The two film types assumed similar crystal structures upon lithiation. High infrared reflectance in the monoclinic phase was described well by an elementary freeelectron plasma edge model. However, the high-Ts. film exhibited significantly poorer reflectance in the infrared when lithiated.

Endovascular procedures for cerebrovenous disorders

Cerebral venous anomalies may have a variety of clinical consequences. MR or CT venogram can assist the imaging diagnosis; yet, cerebral angiogram may be required to confirm or establish the correct diagnosis. Venous anomalies predisposing venous hypertension may be categorized into three major entities such as congenital variations, outflow obstruction, and increased blood flow. The degree of clinical presentations of venous hypertension depends upon the chronicity or acuteness. Venous hypertension may lead to venous congestion with edema, hemorrhage and encephalopathy. Endovascular therapeutic procedures may be employed to relieve venous congestion either from reducing blood flow or relieving obstruction. Those endovascular treatment options include embolization, thrombolysis and angioplastic stentings.

Pyroclastic activity at Home Plate in Gusev Crater, Mars

Home Plate is a layered plateau in Gusev crater on Mars. It is composed of clastic rocks of moderately altered alkali basalt composition, enriched in some highly volatile elements. A coarsegrained lower unit lies under a finer-grained upper unit. Textural observations indicate that the lower strata were emplaced in an explosive event, and geochemical considerations favor an explosive volcanic origin over an impact origin. The lower unit likely represents accumulation of pyroclastic materials, whereas the upper unit may represent eolian reworking of the same pyroclastic materials.

Downregulation of topoisomerase IIbeta in myeloid leukemia cell lines leads to activation of apoptosis following all-trans retinoic acid-induced differentiation/growth arrest

Among the topoisomerase (topo) II isozymes (alpha and beta), topo IIbeta has been suggested to regulate differentiation. In this study, we examined the role of topo IIbeta in all-trans retinoic acid (ATRA)-induced differentiation of myeloid leukemia cell lines. Inhibition of topo IIbeta activity or downregulation of protein expression enhanced ATRA-induced differentiation/growth arrest and apoptosis. ATRA-induced apoptosis in topo IIbeta-deficient cells involved activation of the caspase cascade and was rescued by ectopic expression of topo IIbeta. Gene expression profiling led to the identification of peroxiredoxin 2 (PRDX2) as a candidate gene that was downregulated in topo IIbeta-deficient cells. Reduced expression of PRDX2 validated at the mRNA and protein level, in topo IIbeta-deficient cells correlated with increased accumulation of reactive oxygen species (ROS) following ATRA-induced differentiation. Overexpression of PRDX2 in topo IIbeta-deficient cells led to reduced accumulation of ROS and partially reversed ATRA-induced apoptosis. These results support a role for topo IIbeta in survival of ATRA-differentiated myeloid leukemia cells. Reduced expression of topo IIbeta induces apoptosis in part by impairing the anti-oxidant capacity of the cell owing to downregulation of PRDX2. Thus, suppression of topo IIbeta and/or PRDX2 levels in myeloid leukemia cells provides a novel approach for improving ATRA-based differentiation therapy.

Aeolian processes at the Mars Exploration Rover Meridiani Planum landing site

The martian surface is a natural laboratory for testing our understanding of the physics of aeolian (wind-related) processes in an environment different from that of Earth. Martian surface markings and atmospheric opacity are time-variable, indicating that fine particles at the surface are mobilized regularly by wind. Regolith (unconsolidated surface material) at the Mars Exploration Rover Opportunity's landing site has been affected greatly by wind, which has created and reoriented bedforms, sorted grains, and eroded bedrock. Aeolian features here preserve a unique record of changing wind direction and wind strength. Here we present an in situ examination of a martian bright wind streak, which provides evidence consistent with a previously proposed formational model for such features. We also show that a widely used criterion for distinguishing between aeolian saltation- and suspension-dominated grain behaviour is different on Mars, and that estimated wind friction speeds between 2 and 3 m s(-1), most recently from the northwest, are associated with recent global dust storms, providing ground truth for climate model predictions.

The Opportunity Rover's Athena science investigation at Meridiani Planum, Mars

The Mars Exploration Rover Opportunity has investigated the landing site in Eagle crater and the nearby plains within Meridiani Planum. The soils consist of fine-grained basaltic sand and a surface lag of hematite-rich spherules, spherule fragments, and other granules. Wind ripples are common. Underlying the thin soil layer, and exposed within small impact craters and troughs, are flat-lying sedimentary rocks. These rocks are finely laminated, are rich in sulfur, and contain abundant sulfate salts. Small-scale cross-lamination in some locations provides evidence for deposition in flowing liquid water. We interpret the rocks to be a mixture of chemical and siliciclastic sediments formed by episodic inundation by shallow surface water, followed by evaporation, exposure, and desiccation. Hematite-rich spherules are embedded in the rock and eroding from them. We interpret these spherules to be concretions formed by postdepositional diagenesis, again involving liquid water.

Chemistry of rocks and soils at Meridiani Planum from the Alpha Particle X-ray Spectrometer

The Alpha Particle X-ray Spectrometer on the Opportunity rover determined major and minor elements of soils and rocks in Meridiani Planum. Chemical compositions differentiate between basaltic rocks, evaporite-rich rocks, basaltic soils, and hematite-rich soils. Although soils are compositionally similar to those at previous landing sites, differences in iron and some minor element concentrations signify the addition of local components. Rocky outcrops are rich in sulfur and variably enriched in bromine relative to chlorine. The interaction with water in the past is indicated by the chemical features in rocks and soils at this site.

Soils of Eagle Crater and Meridiani Planum at the Opportunity Rover Landing Site

The soils at the Opportunity site are fine-grained basaltic sands mixed with dust and sulfate-rich outcrop debris. Hematite is concentrated in spherules eroded from the strata. Ongoing saltation exhumes the spherules and their fragments, concentrating them at the surface. Spherules emerge from soils coated, perhaps from subsurface cementation, by salts. Two types of vesicular clasts may represent basaltic sand sources. Eolian ripples, armored by well-sorted hematite-rich grains, pervade Meridiani Planum. The thickness of the soil on the plain is estimated to be about a meter. The flatness and thin cover suggest that the plain may represent the original sedimentary surface.

Jarosite and Hematite at Meridiani Planum from Opportunity's Mössbauer Spectrometer

Mossbauer spectra measured by the Opportunity rover revealed four mineralogical components in Meridiani Planum at Eagle crater: jarosite- and hematite-rich outcrop, hematite-rich soil, olivine-bearing basaltic soil, and a pyroxene-bearing basaltic rock (Bounce rock). Spherules, interpreted to be concretions, are hematite-rich and dispersed throughout the outcrop. Hematitic soils both within and outside Eagle crater are dominated by spherules and their fragments. Olivine-bearing basaltic soil is present throughout the region. Bounce rock is probably an impact erratic. Because jarosite is a hydroxide sulfate mineral, its presence at Meridiani Planum is mineralogical evidence for aqueous processes on Mars, probably under acid-sulfate conditions.

The Spirit Rover's Athena science investigation at Gusev Crater, Mars

The Mars Exploration Rover Spirit and its Athena science payload have been used to investigate a landing site in Gusev crater. Gusev is hypothesized to be the site of a former lake, but no clear evidence for lacustrine sedimentation has been found to date. Instead, the dominant lithology is basalt, and the dominant geologic processes are impact events and eolian transport. Many rocks exhibit coatings and other characteristics that may be evidence for minor aqueous alteration. Any lacustrine sediments that may exist at this location within Gusev apparently have been buried by lavas that have undergone subsequent impact disruption.

Basaltic rocks analyzed by the Spirit Rover in Gusev Crater

The Spirit landing site in Gusev Crater on Mars contains dark, fine-grained, vesicular rocks interpreted as lavas. Pancam and Mini-Thermal Emission Spectrometer (Mini-TES) spectra suggest that all of these rocks are similar but have variable coatings and dust mantles. Magnified images of brushed and abraded rock surfaces show alteration rinds and veins. Rock interiors contain </=25% megacrysts. Chemical analyses of rocks by the Alpha Particle X-ray Spectrometer are consistent with picritic basalts, containing normative olivine, pyroxenes, plagioclase, and accessory FeTi oxides. Mössbauer, Pancam, and Mini-TES spectra confirm the presence of olivine, magnetite, and probably pyroxene. These basalts extend the known range of rock compositions composing the martian crust.

Mineralogy at Gusev Crater from the Mossbauer Spectrometer on the Spirit Rover

Mössbauer spectra measured on Mars by the Spirit rover during the primary mission are characterized by two ferrous iron doublets (olivine and probably pyroxene) and a ferric iron doublet (tentatively associated to nanophase ferric iron oxide). Two sextets resulting from nonstoichiometric magnetite are also present, except for a coating on the rock Mazatzal, where a hematite-like sextet is present. Greater proportions of ferric-bearing phases are associated with undisturbed soils and rock surfaces as compared to fresh rock surfaces exposed by grinding. The ubiquitous presence of olivine in soil suggests that physical rather than chemical weathering processes currently dominate at Gusev crater.

Chemistry of Rocks and Soils in Gusev Crater from the Alpha Particle X-ray Spectrometer

The alpha particle x-ray spectrometer on the Spirit rover determined major and minor elements of soils and rocks in Gusev crater in order to unravel the crustal evolution of planet Mars. The composition of soils is similar to those at previous landing sites, as a result of global mixing and distribution by dust storms. Rocks (fresh surfaces exposed by the rock abrasion tool) resemble volcanic rocks of primitive basaltic composition with low intrinsic potassium contents. High abundance of bromine (up to 170 parts per million) in rocks may indicate the alteration of surfaces formed during a past period of aqueous activity in Gusev crater.

Livestock grazing management and biodiversity conservation in Australian temperate grassy landscapes

There is an increasing interest in the development of livestock grazing management strategies that achieve environmental sustainability and maintain or improve the long-term production capacity of commercial grazing systems. In temperate Australia, these strategies are generally focussed on reducing perennial pasture decline, soil loss, acidity, and salinity. An additional challenge facing land managers and researchers is developing grazing strategies that also maintain and enhance local and regional biodiversity. However, few studies have assessed the compatibility of management practices for maintaining long-term productivity and biodiversity conservation. We still have only a very basic understanding of the effects of different grazing strategies and pasture management on biodiversity and this is a major impediment to the development of appropriate and compatible best management practice. We argue that although there is an increasing desire to find management strategies that protect and enhance biodiversity without hindering long-term agricultural production, in many cases this may not be possible. Current knowledge suggests that compatibility is most likely to be achieved using low-input systems in low productivity (fragile) landscapes, whereas in highly productive (robust) landscapes there is less opportunity for integration of productive land-use and biodiversity conservation. There is an urgent need for improved communication and collaboration between agronomic and ecological researchers and research agencies to ensure that future programs consider sustainability in terms of biodiversity as well as pasture and livestock productivity and soil and water health.